1. Field of the Invention
The present invention relates to an apparatus and method for camera parameter calibration, and more particularly, to an apparatus and method for camera parameter calibration which is capable of easily and simply setting physical and optical characteristic parameters of a camera in order to acquire information on the actual size of objects within an image provided through the camera with high accuracy.
2. Description of the Related Art
With recent rapid development of imaging technologies for security, vision recognition and so on, there have been developed various image processing techniques for analyzing contents of an image obtained through a camera, recognizing objects in the image, and identifying motion of the objects to determine situations occurring in the image, thereby making advanced auto-situation recognition possible.
For example, such image processing techniques provide a function of identifying detected objects from their speed, size and shape to grasp abnormal behaviors or situations of the detected objects, as well as a function of relatively simple image recognition such as recognizing pedestrians in an image or detecting a trespasser entering a particular site.
FIG. 1 shows an example of image processing which is being currently used, where a pedestrian 11 appearing on an image 10 is detected, a mark 12 for detection identification is displayed, and size and moving speed 13 of the pedestrian 11 are detected.
Such image processing requires an object detection function, an object identifying technique, a moving object tracking technique, and a technique for correctly matching objects within an image to information of size in a real space for correct identification and determination of size, speed and the like.
In particular, a space mapping which allows correct measurement of size is essential for precise image analysis, however, for a camera image obtained by projecting a portion of 3-dimensional (3D) space onto a 2-dimensional (2D) space, it is difficult to map a 2D image to a 3D space model without additional information. However, if several parameters used in obtaining the image can be known, it is possible to map the 2D image to the 3D real space by mathematically modeling the 3D real space. Examples of such parameters may mainly include installation height, tilt angle and field of view (FOV) of a camera which captures the image. Correct knowledge of these parameters makes space model configuration by a mathematical modeling possible.
However, for such a space model configuration, since the installation position and tilt angle of the camera must be actually measured, it is not easy to calculate the height and tilt angle of the camera and reliability of calculated actual measurement values is not high due to irregularity of ground and so on. In addition, for FOV, if an auto-focusing function or a zooming function is used for the FOV, it is difficult to obtain correct values of the FOV.
FIG. 2 shows an example of a camera configuration for explaining FOV. As shown, a camera 20 generally includes a lens 21 and an imaging device 22. A distance from the center of the lens 21 to the imaging device 22 is referred to as a focal length (FL) and an optical angle of a region in which an image is formed on the imaging device 22 is referred to as FOV. The FOV may be obtained using the characteristics of the lens 21 and the size and focal length of the imaging device 22. However, all relevant information may not be provided of such camera characteristics and the focal length may be varied if an auto-focusing function is employed, thereby disallowing a user to know such information, of the focal length and so on, which results in difficulty in achieving a correct camera modeling.
After all, since it is difficult for the user to know all of the height, tilt angle and FOV of the camera, a method is being used which actually exposes an object of known size and matches the object within the image to the real object size. However, this method is very inconvenient since the method must be again performed if a monitoring site is changed or a tilt angle is varied.
There is therefore a need for a novel calibration apparatus and method which is capable of more simply and conveniently generating a calibration for mapping an image to a real space model.